First, anyone who has never played the free flash version of flOw should do yourself a favour and give it a go now. It is a small flavour of what you get in the PSN exclusive version of flOw, available for either PS3 and PSP.
I've never played the PS3 version, but judging from online videos and screenshots, flOw for PSP is almost identical to it - save for the lack of 1080p high definition visuals and SIXAXIS controller support. Even with the lower processing capability of the PSP, the results are nothing short of spectacular. Despite being more aliased, the game plays well though it does suffer from very slight frame rate niggles when the screen gets too crowded. Particle effects are handled well, though it is evident that some of them were downgraded from the PS3 version. Despite that the simplistic visuals lend well with the experience.
In flOw you control an aquatic organism via the analogue pad. Objectives or goals do exists, though it is entirely up to you whether you want to participate in them. After 'winning' each level, you will gain the ability to control other organisms. Each of these organisms has their own special skills invoked through either the shoulder button or one of the face buttons.
Your organism can evolve by preying on food. Levels are divided through planes that you access through eating either blue or red orbs. The deeper you go, the more perilous the level becomes. Larger organisms requires you to strategies by hunting down its weak areas. Hunt a food that your organism can't handle and it will get hurt in return. While there are no game overs in flOw, being attacked would usually cause your organism to return to a previous safer plane.
flOw has a unique and serene soundtrack (relative to video gaming) that changes depending on the creature you use and the depth your organism is exploring in. Whenever your organism chomps down its food, tones will ring out, providing the player with a rather euphoric-like chill-out and tranquil audio experience. It is best to play this with a good pair of cans.
This title takes advantage of the PSP's WiFi hardware by supporting local ad-hoc wireless multiplayer. It is very simple, just switch on the WiFi and while at the creature select level, the PSP will automatically connect to other local PSPs. The seamless connectivity is very well done, though unfortunately the game suffers from atrocious frame rate during multiplayer.
flOw isn't by all means perfect but for the cost of a McDonalds 'meal' does provide, in my very honest opinion, a great deal of amount of gameplay that can last anywhere between 1-3 hours to finish depending on how persistent you are. flOw isn't really classifiable as a video game within its traditional definition as it is more of an experience than a conventional game, though it is more of a game than Electroplankton ever was. Some of its fault can be easily be ignored, wile some like the local multiplayer which sounds fun in theory, it is so blighted by problems that should not be shunned. As such I can only recommend flOw as a single player title, one best experienced at the end of each day.